Using biocides

Implementing a preventive treatment as discussed above can often keep the use of biocides (algicides and bactericides) to a minimum (two to six times a year). They can then be reserved for shock treatments when the weather is more propitious to biological growth (spring and fall) or when accidental pollution has occurred. 

However, in petrochemical plants, use of biocides and surfactants is an important part of system protection because of possible process leakage. 

These products act on living cells and their growth in different ways, in particular  

Biocides usually combine several effects. Basically, they can be classified according to two main modes of action  

The biocides in this category are often surfactants and include  

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Alkylbenzyldimethyl quaternaries (ABDM) are used as disinfectants (49) and preservatives. The most effective alkyl chain length for these compounds is between 10 and 18 carbon atoms. Alkyltrimethyl types, alkyl dimethylbenzyl types, and didodecyl dimethyl ammonium chloride [3401-74-9] exhibit excellent germicidal activity (151—159). Dialkyldimethyl types are effective against anaerobic bacteria such as those found in oil wells (94—97). One of the most effective and widely used biocides is didecyl dimethyl ammonium chloride [7173-57-5]. 

Microbiologically influenced souring (MIS) is the production of H2S through the metabolic activities of microorganisms. A better chance for mitigating MIS in some down-hole environments using biocides may be possible if the problem is detected early in the souring process [1259]. However, if the... 

Formaldehyde release biocides are perhaps the most commonly used biocides in metalworking fluids. One of die best know examples of this chemistry is hexahedron -l,3,5-tris(2-hydroxyethyl)-s-triazine, (see Figure 2). 

There are two considerations to be applied when using biocides ... 

Singer H, Muller S, Tixier C, Pillonel L (2002) Triclosan occurrence and fate of a widely used biocide in the aquatic environment field measurements in wastewater treatment plants, surface waters, and lake sediments. Environ Sci Technol 36 4998-5004... 

This study was designed to evaluate the performance of commonly used biocides against the performance of a new liquid blend. In order to choose an effective preservative package, the two main criteria the biocide must have, are (i) to be approved by the US Food and Drug Administration (FDA) under sections 21 CFR 176.170 and 21 CFR 176.180 which cover components of paper and paperboard in contact with foods and (ii) to be designated as a safe biocide (low toxicity, non-sensitiser, easy to handle). The three most commonly used products (i) 5-chloro-2-methyl-4-isothiazolin-3-one + 2-methyl-4-isothiazolin-3-one, (ii) 1,5-pentanedial and (iii) l,2-benzisothiazolin-3-one, currently meet the above criteria. The new liquid blend, l,2-dibromo-2,4-dicyanobutane -I- 2-bro-mo-2-nitropropane-l,3-diol was also designed to meet the criteria. 

Rohrn and Haas was recognized for its development of SEA-N1NE 211 antifouling agent, an effective and more environmentally acceptable ingredient for use in marine antifouling paints, compared with many currently used biocides. 

TixierC., H.P. Singer, S. Canonica, and S.R. Muller (2002). Phototransformation of triclosan in surface waters A relevant elimination process for this widely used biocide-laboratory... 

Although this section has been of necessity very brief, the examples chosen illustrate the advantages which can be obtained by including fluorine atoms in bioactive molecules. In turn, the commercial success in this area is prompting fluorine chemists, both academic and industrial, to seach for ever more selective and economic methods for introducing fluorine atoms into molecules with potentially useful biocidal properties. 

Around the world, the most widely used biocide for industrial cooling systems is gaseous chlorine. Typically, it is a low-cost maintenance item and generally very effective, but may present specific cooling water chemistry limitations, plus possible handling, safety, and environmental problems. (The relatively high capital costs associated with a gaseous chlorine system may also be a problem.)... 

Apart from ready-to-use biocide formulations, there are also other chemicals that exhibit a degree of microbiological control, such as certain corrosion inhibitors that have a biostatic or biocidal action, for example, chromate. 

Gluteraldehyde, a widely used biocide, is not effective in process cooling systems when ammonia leaks reach 50 ppm. Also, do not use gluteraldehyde in water circuits with severe protein contamination (such as can occur in chicken processing plants), as it functions as a protein cross-linking agent and can be overwhelmed. 

Isothiazoline is a widely used biocide, but it is not effective against anaerobic bacteria. It is deactivated by hydrogen sulfide leaks. Also, do not dose to closed systems (because of the presence of 0.2% copper and 2 to 3% magnesium salts, which are used as product stabilizers and can increase the risk of galvanic corrosion). Additionally, the high pH of closed-loop systems will hydrolyze isothiazoline. Automated feed systems may be useful for dosing isothiazolines due to the severe skin irritant nature of this material. 

Trisubstituted organotins are useful biocides in agriculture and industry. They function as fungicides, bactericides, antihelminthics, and rodent repellents (WHO 1980). Tributyltins are used as antifoulants in marine paints but are restricted by the Organotin Antifouling Paints Control Act (June 16, 1988) which limits the type of vessel on which these paints can be used and sets acceptable release limits (U.S. Bureau of Mines 1989). Bis(tributyltin)oxide is used as a preservative for wood products, leather, ropes, fabrics, and paper. 

The oldest and still intensely used biocidal materials release silver ions. Variations in the design of such materials is still the subject of the majority of publications on antimicrobial coatings. The designs cover sparingly soluble silver salts [87], silver nanoparticles [88], silver nanocomposites [89], and elemental silver coatings [32], The release of the silver ions and of other biocides is controlled by the encapsulating matrix, the solubility of the compound, and the material/medium equilibrium constant. 

Waschinski CJ, Zimmermann J, Salz U et al. (2008) Design of contact-active antimicrobial acrylate-based materials using biocidal macromers. Adv Mater 20 104-108... 

Biocidal applications. The use of quaternary ammonium salts in disinfecting systems for household and industrial cleaners has been known for many years [95, 96]. Alkyl-benzyldimethyl quaternaries, alkyltrimethyl quaternaries, and dialkyldimethyl quaternaries are the more commonly used biocidal quaternary ammonium salts [16]. Recently, dialkyldimethyl quaternary ammonium salts have received renewed attention as potential wood preservatives to replace the heavy metal types [97]. Metal-free wood preservative formulations containing dialkyldimethyl ammonium salts with non-halide anions, such as carboxylates, borates, and carbonates, have been developed [98, 99]. 

These mechanisms are of considerable microbiological and biochemical interest, although not all of the above agents find current use as biocides. The plasmid-mediated efflux pumps are particularly important, since efflux is one means whereby acquired resistance to antibiotics occurs (see earlier) and can be a mechanism of resistance to some clinically useful biocides (see later). No efflux pump comparable to those described for arsenate and cadmium [212] has yet been detected in silver-resistant bacteria [213] however, an up-to-date assessment of this subject is available [212]. 

A widely used biocide and preservation product is formaldehyde. Solutions of formaldehyde in water, called formalin, were used for disinfection and conservation, for example, of biological samples for display. Bound formaldehyde is released in small amounts from common easy-care and durable press finishes (Chapter 5). Therefore these finishes include - at least until they are washed - a small antimicrobial side effect. This can also be true for some quaternary compounds, for example wet fastness improvers and softeners. But for more effective requirements specific antimicrobial finishes are necessary. 

Use Biocide for protection of wool, leather, paints, and wood products. 

Typical biocides include hypochlorous acid, chlorine dioxide, hypobromus acid, hydrogen peroxide, ozone, ultraviolet-light treatment, phenolics, aldehydes, and quaternary ammonium compounds (Ref 73, 80). A brief description of each follows (Ref 73, 80). Hypochlorous acid is probably the most commonly used biocide and also one of the most powerful oxidizing agents. The sources of hypochlorous acid are chlorine gas and sodium hypochlorite. In aque-... 

Methods of determining the most commonly used biocides in the indoor environment,... 

Production chemicals are used in relatively much smaller quantities, but significant proportions are discharged into the environment. The chemicals include biocides, scale and corrosion inhibitors, flocculants, surfactants, and paraffin inhibitors. The commonly used biocides include glutaraldehyde, quaternary amine salts, and, to a much smaller extent, some thiocarbamates, isothiazolin, and hypochlorite. Other biocides include Bioban P-1487 (80%... 

Pros and Cons of Some of the Most Frequently Used Biocides... 

Uses Biocide for aq.-based systems (wet state), paints/coatings. inks Features Broad spectrum Aclicide DW [Thor UK[... 

Chem. Descrip. 2-N-Octyl-4-isothiazolin-3-one in Texanol Uses Biocide, algicide. fringicide for dry film protection of aq. and solv.-based coatings, films, and other prods. preservative, biocide, bactericide, fungicide, slimicide for paper/pulp Properties Liq. 15% act. 

Uses Biocide for dry fiim protection of interior/exterior iiq. coatings from surf, fungai and aigai growth Acticide EP Powd. [Thor UK]... 

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